| Step | Hyp | Ref | Expression | 
						
							| 1 |  | elopab | ⊢ ( 𝑝  ∈  { 〈 𝑣 ,  𝑒 〉  ∣  𝑒 : ∅ ⟶ ∅ }  ↔  ∃ 𝑣 ∃ 𝑒 ( 𝑝  =  〈 𝑣 ,  𝑒 〉  ∧  𝑒 : ∅ ⟶ ∅ ) ) | 
						
							| 2 |  | f0bi | ⊢ ( 𝑒 : ∅ ⟶ ∅  ↔  𝑒  =  ∅ ) | 
						
							| 3 |  | opeq2 | ⊢ ( 𝑒  =  ∅  →  〈 𝑣 ,  𝑒 〉  =  〈 𝑣 ,  ∅ 〉 ) | 
						
							| 4 |  | usgr0eop | ⊢ ( 𝑣  ∈  V  →  〈 𝑣 ,  ∅ 〉  ∈  USGraph ) | 
						
							| 5 | 4 | elv | ⊢ 〈 𝑣 ,  ∅ 〉  ∈  USGraph | 
						
							| 6 | 3 5 | eqeltrdi | ⊢ ( 𝑒  =  ∅  →  〈 𝑣 ,  𝑒 〉  ∈  USGraph ) | 
						
							| 7 |  | vex | ⊢ 𝑣  ∈  V | 
						
							| 8 |  | vex | ⊢ 𝑒  ∈  V | 
						
							| 9 | 7 8 | opiedgfvi | ⊢ ( iEdg ‘ 〈 𝑣 ,  𝑒 〉 )  =  𝑒 | 
						
							| 10 |  | id | ⊢ ( 𝑒  =  ∅  →  𝑒  =  ∅ ) | 
						
							| 11 | 9 10 | eqtrid | ⊢ ( 𝑒  =  ∅  →  ( iEdg ‘ 〈 𝑣 ,  𝑒 〉 )  =  ∅ ) | 
						
							| 12 | 6 11 | jca | ⊢ ( 𝑒  =  ∅  →  ( 〈 𝑣 ,  𝑒 〉  ∈  USGraph  ∧  ( iEdg ‘ 〈 𝑣 ,  𝑒 〉 )  =  ∅ ) ) | 
						
							| 13 | 2 12 | sylbi | ⊢ ( 𝑒 : ∅ ⟶ ∅  →  ( 〈 𝑣 ,  𝑒 〉  ∈  USGraph  ∧  ( iEdg ‘ 〈 𝑣 ,  𝑒 〉 )  =  ∅ ) ) | 
						
							| 14 | 13 | adantl | ⊢ ( ( 𝑝  =  〈 𝑣 ,  𝑒 〉  ∧  𝑒 : ∅ ⟶ ∅ )  →  ( 〈 𝑣 ,  𝑒 〉  ∈  USGraph  ∧  ( iEdg ‘ 〈 𝑣 ,  𝑒 〉 )  =  ∅ ) ) | 
						
							| 15 |  | eleq1 | ⊢ ( 𝑝  =  〈 𝑣 ,  𝑒 〉  →  ( 𝑝  ∈  USGraph  ↔  〈 𝑣 ,  𝑒 〉  ∈  USGraph ) ) | 
						
							| 16 |  | fveqeq2 | ⊢ ( 𝑝  =  〈 𝑣 ,  𝑒 〉  →  ( ( iEdg ‘ 𝑝 )  =  ∅  ↔  ( iEdg ‘ 〈 𝑣 ,  𝑒 〉 )  =  ∅ ) ) | 
						
							| 17 | 15 16 | anbi12d | ⊢ ( 𝑝  =  〈 𝑣 ,  𝑒 〉  →  ( ( 𝑝  ∈  USGraph  ∧  ( iEdg ‘ 𝑝 )  =  ∅ )  ↔  ( 〈 𝑣 ,  𝑒 〉  ∈  USGraph  ∧  ( iEdg ‘ 〈 𝑣 ,  𝑒 〉 )  =  ∅ ) ) ) | 
						
							| 18 | 17 | adantr | ⊢ ( ( 𝑝  =  〈 𝑣 ,  𝑒 〉  ∧  𝑒 : ∅ ⟶ ∅ )  →  ( ( 𝑝  ∈  USGraph  ∧  ( iEdg ‘ 𝑝 )  =  ∅ )  ↔  ( 〈 𝑣 ,  𝑒 〉  ∈  USGraph  ∧  ( iEdg ‘ 〈 𝑣 ,  𝑒 〉 )  =  ∅ ) ) ) | 
						
							| 19 | 14 18 | mpbird | ⊢ ( ( 𝑝  =  〈 𝑣 ,  𝑒 〉  ∧  𝑒 : ∅ ⟶ ∅ )  →  ( 𝑝  ∈  USGraph  ∧  ( iEdg ‘ 𝑝 )  =  ∅ ) ) | 
						
							| 20 |  | fveqeq2 | ⊢ ( 𝑔  =  𝑝  →  ( ( iEdg ‘ 𝑔 )  =  ∅  ↔  ( iEdg ‘ 𝑝 )  =  ∅ ) ) | 
						
							| 21 | 20 | elrab | ⊢ ( 𝑝  ∈  { 𝑔  ∈  USGraph  ∣  ( iEdg ‘ 𝑔 )  =  ∅ }  ↔  ( 𝑝  ∈  USGraph  ∧  ( iEdg ‘ 𝑝 )  =  ∅ ) ) | 
						
							| 22 | 19 21 | sylibr | ⊢ ( ( 𝑝  =  〈 𝑣 ,  𝑒 〉  ∧  𝑒 : ∅ ⟶ ∅ )  →  𝑝  ∈  { 𝑔  ∈  USGraph  ∣  ( iEdg ‘ 𝑔 )  =  ∅ } ) | 
						
							| 23 | 22 | exlimivv | ⊢ ( ∃ 𝑣 ∃ 𝑒 ( 𝑝  =  〈 𝑣 ,  𝑒 〉  ∧  𝑒 : ∅ ⟶ ∅ )  →  𝑝  ∈  { 𝑔  ∈  USGraph  ∣  ( iEdg ‘ 𝑔 )  =  ∅ } ) | 
						
							| 24 | 1 23 | sylbi | ⊢ ( 𝑝  ∈  { 〈 𝑣 ,  𝑒 〉  ∣  𝑒 : ∅ ⟶ ∅ }  →  𝑝  ∈  { 𝑔  ∈  USGraph  ∣  ( iEdg ‘ 𝑔 )  =  ∅ } ) | 
						
							| 25 | 24 | ssriv | ⊢ { 〈 𝑣 ,  𝑒 〉  ∣  𝑒 : ∅ ⟶ ∅ }  ⊆  { 𝑔  ∈  USGraph  ∣  ( iEdg ‘ 𝑔 )  =  ∅ } | 
						
							| 26 |  | eqid | ⊢ { 〈 𝑣 ,  𝑒 〉  ∣  𝑒 : ∅ ⟶ ∅ }  =  { 〈 𝑣 ,  𝑒 〉  ∣  𝑒 : ∅ ⟶ ∅ } | 
						
							| 27 | 26 | griedg0prc | ⊢ { 〈 𝑣 ,  𝑒 〉  ∣  𝑒 : ∅ ⟶ ∅ }  ∉  V | 
						
							| 28 |  | prcssprc | ⊢ ( ( { 〈 𝑣 ,  𝑒 〉  ∣  𝑒 : ∅ ⟶ ∅ }  ⊆  { 𝑔  ∈  USGraph  ∣  ( iEdg ‘ 𝑔 )  =  ∅ }  ∧  { 〈 𝑣 ,  𝑒 〉  ∣  𝑒 : ∅ ⟶ ∅ }  ∉  V )  →  { 𝑔  ∈  USGraph  ∣  ( iEdg ‘ 𝑔 )  =  ∅ }  ∉  V ) | 
						
							| 29 | 25 27 28 | mp2an | ⊢ { 𝑔  ∈  USGraph  ∣  ( iEdg ‘ 𝑔 )  =  ∅ }  ∉  V | 
						
							| 30 |  | df-3an | ⊢ ( ( 𝑔  ∈  USGraph  ∧  0  ∈  ℕ0*  ∧  ∀ 𝑣  ∈  ( Vtx ‘ 𝑔 ) ( ( VtxDeg ‘ 𝑔 ) ‘ 𝑣 )  =  0 )  ↔  ( ( 𝑔  ∈  USGraph  ∧  0  ∈  ℕ0* )  ∧  ∀ 𝑣  ∈  ( Vtx ‘ 𝑔 ) ( ( VtxDeg ‘ 𝑔 ) ‘ 𝑣 )  =  0 ) ) | 
						
							| 31 | 30 | bicomi | ⊢ ( ( ( 𝑔  ∈  USGraph  ∧  0  ∈  ℕ0* )  ∧  ∀ 𝑣  ∈  ( Vtx ‘ 𝑔 ) ( ( VtxDeg ‘ 𝑔 ) ‘ 𝑣 )  =  0 )  ↔  ( 𝑔  ∈  USGraph  ∧  0  ∈  ℕ0*  ∧  ∀ 𝑣  ∈  ( Vtx ‘ 𝑔 ) ( ( VtxDeg ‘ 𝑔 ) ‘ 𝑣 )  =  0 ) ) | 
						
							| 32 | 31 | a1i | ⊢ ( 𝑔  ∈  USGraph  →  ( ( ( 𝑔  ∈  USGraph  ∧  0  ∈  ℕ0* )  ∧  ∀ 𝑣  ∈  ( Vtx ‘ 𝑔 ) ( ( VtxDeg ‘ 𝑔 ) ‘ 𝑣 )  =  0 )  ↔  ( 𝑔  ∈  USGraph  ∧  0  ∈  ℕ0*  ∧  ∀ 𝑣  ∈  ( Vtx ‘ 𝑔 ) ( ( VtxDeg ‘ 𝑔 ) ‘ 𝑣 )  =  0 ) ) ) | 
						
							| 33 |  | 0xnn0 | ⊢ 0  ∈  ℕ0* | 
						
							| 34 |  | ibar | ⊢ ( ( 𝑔  ∈  USGraph  ∧  0  ∈  ℕ0* )  →  ( ∀ 𝑣  ∈  ( Vtx ‘ 𝑔 ) ( ( VtxDeg ‘ 𝑔 ) ‘ 𝑣 )  =  0  ↔  ( ( 𝑔  ∈  USGraph  ∧  0  ∈  ℕ0* )  ∧  ∀ 𝑣  ∈  ( Vtx ‘ 𝑔 ) ( ( VtxDeg ‘ 𝑔 ) ‘ 𝑣 )  =  0 ) ) ) | 
						
							| 35 | 33 34 | mpan2 | ⊢ ( 𝑔  ∈  USGraph  →  ( ∀ 𝑣  ∈  ( Vtx ‘ 𝑔 ) ( ( VtxDeg ‘ 𝑔 ) ‘ 𝑣 )  =  0  ↔  ( ( 𝑔  ∈  USGraph  ∧  0  ∈  ℕ0* )  ∧  ∀ 𝑣  ∈  ( Vtx ‘ 𝑔 ) ( ( VtxDeg ‘ 𝑔 ) ‘ 𝑣 )  =  0 ) ) ) | 
						
							| 36 |  | eqid | ⊢ ( Vtx ‘ 𝑔 )  =  ( Vtx ‘ 𝑔 ) | 
						
							| 37 |  | eqid | ⊢ ( VtxDeg ‘ 𝑔 )  =  ( VtxDeg ‘ 𝑔 ) | 
						
							| 38 | 36 37 | isrusgr0 | ⊢ ( ( 𝑔  ∈  USGraph  ∧  0  ∈  ℕ0* )  →  ( 𝑔  RegUSGraph  0  ↔  ( 𝑔  ∈  USGraph  ∧  0  ∈  ℕ0*  ∧  ∀ 𝑣  ∈  ( Vtx ‘ 𝑔 ) ( ( VtxDeg ‘ 𝑔 ) ‘ 𝑣 )  =  0 ) ) ) | 
						
							| 39 | 33 38 | mpan2 | ⊢ ( 𝑔  ∈  USGraph  →  ( 𝑔  RegUSGraph  0  ↔  ( 𝑔  ∈  USGraph  ∧  0  ∈  ℕ0*  ∧  ∀ 𝑣  ∈  ( Vtx ‘ 𝑔 ) ( ( VtxDeg ‘ 𝑔 ) ‘ 𝑣 )  =  0 ) ) ) | 
						
							| 40 | 32 35 39 | 3bitr4d | ⊢ ( 𝑔  ∈  USGraph  →  ( ∀ 𝑣  ∈  ( Vtx ‘ 𝑔 ) ( ( VtxDeg ‘ 𝑔 ) ‘ 𝑣 )  =  0  ↔  𝑔  RegUSGraph  0 ) ) | 
						
							| 41 | 40 | rabbiia | ⊢ { 𝑔  ∈  USGraph  ∣  ∀ 𝑣  ∈  ( Vtx ‘ 𝑔 ) ( ( VtxDeg ‘ 𝑔 ) ‘ 𝑣 )  =  0 }  =  { 𝑔  ∈  USGraph  ∣  𝑔  RegUSGraph  0 } | 
						
							| 42 |  | usgr0edg0rusgr | ⊢ ( 𝑔  ∈  USGraph  →  ( 𝑔  RegUSGraph  0  ↔  ( Edg ‘ 𝑔 )  =  ∅ ) ) | 
						
							| 43 |  | usgruhgr | ⊢ ( 𝑔  ∈  USGraph  →  𝑔  ∈  UHGraph ) | 
						
							| 44 |  | uhgriedg0edg0 | ⊢ ( 𝑔  ∈  UHGraph  →  ( ( Edg ‘ 𝑔 )  =  ∅  ↔  ( iEdg ‘ 𝑔 )  =  ∅ ) ) | 
						
							| 45 | 43 44 | syl | ⊢ ( 𝑔  ∈  USGraph  →  ( ( Edg ‘ 𝑔 )  =  ∅  ↔  ( iEdg ‘ 𝑔 )  =  ∅ ) ) | 
						
							| 46 | 42 45 | bitrd | ⊢ ( 𝑔  ∈  USGraph  →  ( 𝑔  RegUSGraph  0  ↔  ( iEdg ‘ 𝑔 )  =  ∅ ) ) | 
						
							| 47 | 46 | rabbiia | ⊢ { 𝑔  ∈  USGraph  ∣  𝑔  RegUSGraph  0 }  =  { 𝑔  ∈  USGraph  ∣  ( iEdg ‘ 𝑔 )  =  ∅ } | 
						
							| 48 | 41 47 | eqtri | ⊢ { 𝑔  ∈  USGraph  ∣  ∀ 𝑣  ∈  ( Vtx ‘ 𝑔 ) ( ( VtxDeg ‘ 𝑔 ) ‘ 𝑣 )  =  0 }  =  { 𝑔  ∈  USGraph  ∣  ( iEdg ‘ 𝑔 )  =  ∅ } | 
						
							| 49 |  | neleq1 | ⊢ ( { 𝑔  ∈  USGraph  ∣  ∀ 𝑣  ∈  ( Vtx ‘ 𝑔 ) ( ( VtxDeg ‘ 𝑔 ) ‘ 𝑣 )  =  0 }  =  { 𝑔  ∈  USGraph  ∣  ( iEdg ‘ 𝑔 )  =  ∅ }  →  ( { 𝑔  ∈  USGraph  ∣  ∀ 𝑣  ∈  ( Vtx ‘ 𝑔 ) ( ( VtxDeg ‘ 𝑔 ) ‘ 𝑣 )  =  0 }  ∉  V  ↔  { 𝑔  ∈  USGraph  ∣  ( iEdg ‘ 𝑔 )  =  ∅ }  ∉  V ) ) | 
						
							| 50 | 48 49 | ax-mp | ⊢ ( { 𝑔  ∈  USGraph  ∣  ∀ 𝑣  ∈  ( Vtx ‘ 𝑔 ) ( ( VtxDeg ‘ 𝑔 ) ‘ 𝑣 )  =  0 }  ∉  V  ↔  { 𝑔  ∈  USGraph  ∣  ( iEdg ‘ 𝑔 )  =  ∅ }  ∉  V ) | 
						
							| 51 | 29 50 | mpbir | ⊢ { 𝑔  ∈  USGraph  ∣  ∀ 𝑣  ∈  ( Vtx ‘ 𝑔 ) ( ( VtxDeg ‘ 𝑔 ) ‘ 𝑣 )  =  0 }  ∉  V |